Mankind has evolved over millions and millions of years from the single-celled water bound organisms, to primitive primates and then to apes. Venturing out of the forests, early man started to walk on two feet and exposing the scalp to the harsh rays of the sun.

Radiation from the sun is harmful and can cause free-radical damage. Free radicals are highly reactive substances which can occur in the body under certain conditions, such as over-exposure to UV light. Free radicals react with the body to cause damage to many bodily systems in comes into contact with which speeds the ageing process.

Thick hair of the scalp on a person signifies much protection from solar radiation and therefore minimising the risk of free radical damage and premature ageing. Our prehistoric ancestors were very attracted to someone with thick hair as a potential mate. The likelihood is that the person with the thick hair had the genes for thick hair as well and passed this natural sun protection to his/her offspring and increasing their chances of a long life in which to procreate.

If however, the person displaying a thick head of hair did not have the genes for thick hair, this is not to say that he or she is less of an attractive offer. Hair is made of protein, predominantly of a protein called keratin. Rich sources of protein include meat and eggs. If a person had thick hair, it meant there was a protein rich diet and the only people with a protein rich diet were the best hunter-gatherers. They also had the best overall health since their diet was good. They made brilliant mates since it would mean that the offspring would be well fed.

The pigmentation in the hair is also a protein. It is a protein called melanin. Therefore, people with very dark hair (for their hair colour) were the people with a protein rich diet. Prehistoric man found dark hair very attractive because of this sign of a rich diet. Melanin is the substance in the body which prevents UV light damaging the skin, so dark haired people had extra protection and were likely to live longer and have more children.

One thing that humans still did in its early developement, was social grooming, just like our ape cousins. Social grooming cemented relationships between all members of the family and contributed to lower stress levels and overall wellbeing. Of course, playing with someones hair could lead to other things, like sex, because its tactile nature can be sexually stimulating. Thick hair on the scalp lends itself well to social grooming and of course increased the likelihood of sex and more offspring were produced.

So, why can a thick head of hair play an important role in human evolution? Well, it impresses the animal urges in us and can lead to a long and healthy sex life.